Article: http://www.zzzprojects.com/entity-framework/how/performance-detectchanges

entity-framework-how-performance-detectchanges-example-1.cs

using (var ctx = new CustomerContext())
{
    foreach(var line in lines)
    {
        var customer = new Customer();
        // ...code...
        
        // DetectChanges is invoked every time you call Add
        ctx.Customers.Add(customer);
    }
    
    ctx.SaveChanges();
}

entity-framework-how-performance-detectchanges-example-2.cs

// 1. CREATE batchSize variable
int batchSize = 1000;

var ctx = new CustomerContext();
for (int i = 0; i < lines.Count; i++)
{
    // 2. CALL SaveChanges before creating a new batch
    if (i != 0 && i%batchSize == 0)
    {
        ctx.SaveChanges();
        ctx = new CustomerContext();
    }

    var customer = new Customer();
    // ...code...
    ctx.Customers.Add(customer);
}

// 3. CALL SaveChanges
ctx.SaveChanges();

// 4. Done!

entity-framework-how-performance-detectchanges-example-3.cs

using (var ctx = new CustomerContext())
{
    // 1. CREATE a list
    List<Customer> customers = new List<Customer>();
    
    foreach(var line in lines)
    {
        var customer = new Customer();
        // ...code...
        
        // 2. ADD entity to the list
        customers.Add(customer);
    }
    
    // 3. USE AddRange with the list
    ctx.Customers.AddRange(customers);
    
    // 4. SaveChanges
    ctx.SaveChanges();
    
    // 5. Done!
}

entity-framework-how-performance-detectchanges-example-4.cs

using (var ctx = new CustomerContext())
{
    // 1. SET AutoDetectChangesEnabled = false
    ctx.Configuration.AutoDetectChangesEnabled = false;
     
    foreach(var line in lines)
    {
        var customer = new Customer();
        // ...code...
        ctx.Customers.Add(customer);
    }
    
    // 2. CALL DetectChanges before SaveChanges
    ctx.ChangeTracker.DetectChanges();
    
    // 3. SaveChanges
    ctx.SaveChanges();
    
    // 4. Done!
}

entity-framework-how-performance-detectchanges-example-5.cs

using (var ctx = new EF6.CustomerContext())
{
	for(int i = 0; i < lines.Count; i++)
	{
		ctx.Customers.Add(customer);
	}
}

entity-framework-how-performance-detectchanges-example-6.cs

internal virtual void DetectChanges()
{
    IList<EntityEntry> entityEntriesForDetectChanges = this.GetEntityEntriesForDetectChanges();
    if ((entityEntriesForDetectChanges != null) && this.TransactionManager.BeginDetectChanges())
    {
        try
        {
            DetectChangesInNavigationProperties(entityEntriesForDetectChanges);
            DetectChangesInScalarAndComplexProperties(entityEntriesForDetectChanges);
            DetectChangesInForeignKeys(entityEntriesForDetectChanges);
            this.DetectConflicts(entityEntriesForDetectChanges);
            this.TransactionManager.BeginAlignChanges();
            this.AlignChangesInRelationships(entityEntriesForDetectChanges);
        }
        finally
        {
            this.TransactionManager.EndAlignChanges();
            this.TransactionManager.EndDetectChanges();
        }
    }
}